Multi-field formulation of gravitational particle production after inflation

Understand

We study multi-field inflation models that contain a non-trivial field-space metric and a non-minimal coupling between the gravity and inflaton sectors.

• In such models it is known that even in the absence of explicit interaction terms the inflaton sector can decay into matter as a result of its non-minimal coupling to gravity, thereby reheating the Universe gravitationally.
• Using the Bogoliubov approach we evaluate the gravitational decay rates of the inflaton fields into both scalars and fermions, and analyse the reheating dynamics.
• We also discuss how the interpretation of the reheating dynamics differs in the so-called Jordan and Einstein frames, highlighting that the calculation of the Bogoliubov coefficients is independent of the frame in which one starts.